rmalhotra has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (hashes)

Is there any way to get the key corresponding to a given value from a hash table

Originally posted as a Categorized Question.

  • Comment on Get the Key corresponding to any given value

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Re: Get the Key corresponding to any given value⭐
by jsprat (Curate) on Jun 28, 2002 at 18:18 UTC
    If the values are unique:

    my %rhash = reverse %hash;
my $key = $rhash{$value};

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    will give you the key for a given value.

    If you might have duplicate values, grep is your friend: 

    my @keys = grep { $hash{$_} eq $value } keys %hash;

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    If your values are numeric, use "==" instead of eq.
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Re: Get the Key corresponding to any given value⭐
by manav (Scribe) on Mar 01, 2005 at 18:07 UTC
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Re: Get the Key corresponding to any given value
by codeacrobat (Chaplain) on Mar 26, 2006 at 10:51 UTC 
    %h=(1 => 2,
    3 => 2,
    4 => 3);

$val = 2;

# use eq for strings, or whatever equals method for objects
@keys = grep {$h{$_} == $val} keys %h; # (1,3)

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    Originally posted as a Categorized Answer.

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Re: Get the Key corresponding to any given value
by simmisam (Novice) on Jan 17, 2014 at 06:54 UTC 
    my ($key) = grep {$value ~~ $hash{$_}} keys %hash;
print "Key = $key\n";

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      values are not necessarily unique so the left hand side should be a list.

      and using smart match doesn't make sense, better decide if == or eq are appropriate.

      simmisam did you notice that most of your recent answers in this category were rejected by QandAEditors b/c of poor quality?

      And (sadly) I have to say, I hope this one too!

      Maybe you should stop playing this game till you are more experienced?

      Cheers Rolf

      ( addicted to the Perl Programming Language)

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        I'm actually OK with this one, but I would prefer that he would include an explanation of the value of his approach, i.e. describe the situations in which he thinks it could be useful.

        I reckon we are the only monastery ever to have a dungeon stuffed with 16,000 zombies.
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